In various semiconductor manufacturing processes, a planarized wafer surface is of prime importance for the miniaturization and high density of semiconductor devices. A conventional method for planarizing the wafer surface is a chemical mechanical polishing (CMP) method which adds polishing slurry between a wafer surface to be polished and a polishing pad, so as to planarize the wafer surface by using a combined effect of mechanical friction and chemical reactions between the polishing slurry and the wafer surface. The conventional CMP method is a dissociation abrasive polishing method, in which the abrasives included in the polishing slurry are randomly distributed on the polishing pad. The abrasives have a non-uniform distribution density, which may result in adverse polishing effects, a low utilization ratio, environmental pollutions caused by the dumped slurry, and the like. Therefore, the free abrasive polishing method has been gradually replaced by a fixed abrasive polishing method.
In the fixed abrasive polishing method, the abrasives and the polishing pad are combined together to form a fixed abrasive pad with a uniformly concave-convex patterned surface. Referring to FIG. 1, a conventional fixed abrasive polishing method includes conveying a polishing pad 102 to a polishing platen 101 by an input roller 105a and an output roller 105b, supplying a surface of the polishing pad 102 with a polishing slurry solution, mounting a wafer 103 to a polishing head 104, which forces the wafer surface downwardly to make contact with an abrasive layer of the polishing pad 102, and starting a driving power to rotate the polishing platen 101 through a bearing 100 and the wafer 103 through the polishing head 104. The polishing platen 101 moves relative to the wafer 103, and rubs the surface of the wafer 103 against the abrasive layer on the surface of the polishing pad 102, so that the surface of the wafer 103 is polished. In this polishing process, only the projections (referred as abrasive blocks herein) attached on the polishing pad 102 have contact with the surface of the wafer 103, so that a contact surface area between the polishing slurry and the wafer is smaller than a contact surface area in the conventional free abrasive polishing method. The smaller contact surface area may result in a greater pressure therein. Accordingly, the above-described CMP process may require a faster polishing speed to obtain a desired polishing effect. The over polish window may be enlarged, which may greatly reduce the erosions and dishing problems, so that the product yield can be improved. Moreover, because the polishing speed has a high selectivity to the surface topography of the wafer, a desired polishing effect may be achieved by removing fewer wafer materials, thus reduces the production cost. Moreover, the polishing speed may vary according to different chemical agents added into the polishing process. With the continuous development of semiconductor manufacturing technology, the critical dimensions of semiconductor devices are getting smaller continuously, so the fixed abrasive polishing method becomes more and more important.
However, when applying the fixed abrasive polishing method, the abrasive blocks fixed on the polishing pad are continuously consumed until scrapped, as the polishing process goes on. The quality of the abrasive blocks may affect the polishing quality greatly. The consumption or damage of the abrasive blocks can cause a decrease in removal rates and an increase in scratches, which renders the polishing process unstable. Therefore, obtaining a stable polishing performance has been a significant problem for the fixed abrasive polishing method.
US Patent Publication No. 20020049027 to Walker et al. discloses methods and apparatus using a fixed abrasive polishing pad to perform mechanical polishing of a article surface. However, this patent only partially solves the above described problems.